Abstract

Optical micro-angiography (OMAG) was developed to achieve volumetric imaging of the microstructures and dynamic cerebrovascular blood perfusion in mice with capillary level resolution and high signal-to-background ratio. In this paper, we present a high-speed and high-sensitivity OMAG imaging system by using an InGaAs line scan camera and broadband light source at 1.3 µm wavelength for enhanced imaging depth in tissue. We show that high quality imaging of cerebrovascular blood perfusion down to capillary level resolution with the intact skin and cranium are obtained in vivo with OMAG, without the interference from the blood perfusion in the overlaying skin. The results demonstrate the potential of 1.3µm OMAG for high-speed and high-sensitivity imaging of blood perfusion in human and small animal studies.

In vivo imaging of the finger nail bed of an adult volunteer (41 years age). Shown is a B scan consisting of 1000 A scans across 2.5mm. (A) Structural OCT/OMAG image where the nail plate and bed can be clearly visualized. (B) OMAG flow image where it is evident that the capillary blood flows within nail bed are abundant. The white bar indicates 500µm.

Cut away view of volume image rendered from 3-D micro-structural images of the mouse head obtained by OMAG system in vivo, where the important tissue layers, such as skin, skull bone and grey matter are clearly identified. The volume image given has a physical dimension of 2.5×2.5×2.0 mm3 in x-y-z direction as shown. See also the movie (2.5Mbytes); [Media 1]

Cerebral blood perfusion was imaged with OMAG in vivo with the intact skin and cranium. (A) volumetric rendering of fused 3D OMAG micro-structural and blood perfusion image. The volume size is 2.5×2.5×2.0 mm3, see also the associated movie for details (2.6Mbytes) [Media 2]; (B) projection image of blood flows from within the skin; (C) projection image of cerebro-vascular perfusion from brain cortex; and (D) Projection image from all depths.

The head of an adult mouse with the skin and skull intact was imaged with OMAG in vivo. (A) and (B) are the projection views of blood perfusion from within the skin and the brain cortex, respectively. Capillary blood flow can be seen from (B). It took ~7.5 minutes to acquire the 3-D data to obtain (A) and (B) using the current system setup. (C) Photograph taken right after the experiments where viewing the vasculatures through the skin is impossible. (D) Photograph showing blood vessels over the cortex after the skull and the skin of the same mouse were carefully removed. The superficial major blood vessels show excellent correspondence with those in (B). The area marked with dashed white box represents 4.2 by 7.2 mm2; and the scale bar indicates 1.0 mm.